Field of the Invention
The present invention relates to a technique for controlling communication between a server on a network and a network device.
Description of the Related Art
In a client/server system under Internet environment, it is impossible to transmit data from a server which is the transmission source of various print services to a client-side image forming device which is the execution source of various print services due to firewall. Accordingly, there has been proposed a polling-type communication method in which the inquiry about the presence or absence of a command is made from a client-side image forming device to a server which is the transmission source of various print services. Japanese Patent Laid-Open No. 2007-334612 discloses a device management system in which upon receiving an inquiry about the presence or absence of an instruction across a firewall from a managed device, a management device sends the instruction as a reply to the inquiry in a session established upon reception of the inquiry.
A communication method (Push communication method) that performs Push communication from a server (management device) on the Internet to a network device on an intra-network within a firewall, starting from initial communication (Handshake) from a client, is contemplated. The Push communication method is a communication method that allows the provision of an instruction from a management device without an instruction request (HTTP request or the like) from within a firewall. The Push communication method includes, for example, a protocol (RFC 6455) called “WebSocket”.
The management device can distribute a command in real time by communicating in the Push communication method, which eliminates the need for a polling inquiry about the presence or absence of a command in a polling scheme from a network device to a management device. In other words, with the aid of Push communication, the time loss caused by the interval of polling, which have been occurred in prior art, can be eliminated.
However, Push communication has a feature which consistently retains communication connection between network devices and management devices. Thus, in the system in which the upper limit of the number of communication connections between network devices and management devices is set from the viewpoint of cost or the like, the number of connections readily reaches the upper limit value. Consequently, there may be a case where Push communication cannot be established (Handshake cannot be started) between network devices and management devices.